This project aims at elucidating the biological function(s) of the normal human c-fps/fes proto-oncogene, and to understand the molecular basis of its oncogenic potential. We have generated a cDNA copy of human c-fps/fes from a genomic DNA by means of a retroviral shuttle vector, and have begun characterization of its biological and biochemical properties. The rescued cDNA encoded an NCP92 protein that was indistinguishable from myeloid cell NCP92, providing direct evidence that this 92 Kda cellular tyrosine kinase is the gene product of human c-fps/fes. We also showed that human c-fps/fes is susceptible to oncogenic activation by N-terminal linkage with viral gag sequences.